Association of the G2014G genotype in estrogen receptor 1 gene with failure of the mifepristone-induced termination of early pregnancy.

Mifepristone is a synthetic steroid compound that has been applied to terminate early pregnancy for many years. However, about 15% of the women undergo failure in termination of early pregnancy, the causes of which remain largely unknown. We herein selected estrogen receptor 1 gene (ESR1) as a candidate gene to determine whether single nuclear polymorphisms (SNPs) in ESR1 were associated with the failure of mifepristone-induce abortion. The subjects recruited were 30 subjects that failed to abort and 60 subjects with a successful medical abortion. Three SNPs, T-397C (rs2234693), C325G (rs1801132), and G2014A (rs2228480), were analyzed by PCR, followed by restriction fragment length polymorphism (RFLP) analysis. The latter two polymorphic sites are located in the protein-coding region, but do not alter the amino acid. Among the three SNPs examined, we found the significant role of the G2014A polymorphism; namely, the distribution of the GG, AG and AA genotypes was different between the failure group and the success group. The frequency of the GG (G2014G) genotype was higher in the failure group (86.7%) than that in the success group (60.0%) (p = 0.030), while the frequency of the G2014A heterozygote was lower in the failure group (6.7%) than in the success group (28.3%) (p = 0.013). Moreover, the frequency of the G allele was higher in the failure group (90%) and lower in the success group (10.0%) (p = 0.013). These results indicate that the GG genotype of the G2014A polymorphism is associated with the risk of failure in the mifepristone-induced abortion.